Ring materials and specifications

Rings can also be supplied to EN and DIN forging grades and to the customer's own material specification, on enquiry.

Types of rings

• Seamless rolled rings – a forged and pierced blank is rolled between a driven roll and an idler roll to increase its diameter and reduce its wall. Rolling gives a continuous circumferential grain flow, which improves strength and fatigue resistance. Rolled rings are used for large flanges, bearing races, gear blanks and slewing rings.
• Open-die forged rings – forged over a mandrel from a pierced billet, for thick-walled and smaller-diameter rings and for alloys or sizes not suited to ring rolling.
• Plate-cut rings – cut from plate by plasma, oxy-fuel or water-jet, for flat rings, spacers, stiffening rings and low-stress parts. They do not have the grain flow of forged rings and are not used where forging is specified.

How we manufacture forged rings

The process starts with a billet of certified material, cut to the weight needed for the finished ring plus machining allowance. The billet is heated, upset and pierced to form a doughnut-shaped preform, which is then forged over a mandrel or rolled to the required outside diameter, inside diameter and height. After forging, the ring is heat treated to the condition the specification requires – solution annealing for stainless and duplex steel, normalising or normalising and tempering for carbon steel, and normalising and tempering or quenching and tempering for alloy steel.

Rings are then rough machined or finish machined to drawing. Test pieces for chemical and mechanical testing are taken from the ring or from a prolongation forged with it, as the specification and order require.

Sizes, condition and testing

Please send a drawing or the finished and as-supplied dimensions, with the material specification, heat-treatment condition, testing and quantity.

Rough-machined rings are supplied with an allowance on every surface for the customer's final machining, which also removes the forging skin and any surface decarburisation. Finish-machined rings are supplied ready for use or for final assembly, with surface finish and tolerances to the drawing.

Choosing the material

Carbon steel A105 rings are used for flange blanks and vessel parts in ambient and higher-temperature service, and A350 LF2 where impact testing at low temperature is required. A694 high-yield forgings are used for pipeline flanges and fittings. Alloy steels F11 and F22 are chosen for high-temperature steam and refinery service, and F91 for the most demanding power plant conditions. Stainless steel F304L and F316L rings are used for chemical, pharmaceutical and food equipment, and duplex F51 and super duplex F53 and F55 for seawater and chloride service. Nickel alloy rings to ASTM B564 are used for highly corrosive chemical service and for high-temperature components. Sour-service rings can be supplied to NACE MR0175 / ISO 15156 on request.

Applications

• Blanks for large-diameter and special flanges, girth flanges and body flanges of pressure vessels and heat exchangers
• Bearing races, gear rings and slewing rings for heavy machinery, wind turbines and cranes
• Valve seats, bonnets and body rings
• Pump and compressor casings, wear rings and seal rings
• Turbine and generator components in power plants
• Stiffening rings, spacers and support rings in fabrication

Quality and traceability

Each ring is marked with the material grade, heat number and a unique identification, so it can be traced to its billet, heat-treatment batch and test results. Dimensional inspection is carried out against the drawing, and the mill test certificate reports chemical composition, mechanical properties and heat treatment. Third-party inspection by the customer's nominated agency can be arranged on request. Our company is certified to ISO 9001:2015, ISO 14001:2015 and ISO 45001:2018.

Related products

Rings are closely related to our flanges, which are often machined from forged rings, and to our round bars, from which smaller rings are made. Flat rings and washers can also be cut from circles. Every product form is listed on the products page.